Countersinking drill



April 3, 1945. D. H. FREESE 2,372,719

NNNNNNNNNNNNNNNNN LL v Dazylasflfieesq,

'INVENTOR.

Patented Apr. 3, 1945 UNITED STATES PATENT OFFICE 1 Claim.

My invention relates to the forming of counter sunk bolt and rivet holesin metallic parts, and has among its objects and advantages theprovision of an improved countersinking drill whereby aligned holes maybe simultaneously bored in the work in a single continuous operation.

In the accompanying drawing:

Figure l is a viewer a conventional drill showing my inventionincorporated therein;

Figure 2 is a view of the same drill rotated ninety degrees; and 1Figure 3 is a sectional View taken along the line 3-3 of Figure 1.

In the embodiment of the invention selected for illustration, I make useof a conventional drill ID to which I attach two countersinkingformations l2. The formations l2 are identical and each comprises ametallic body having a curved face [4 shaped to fit in the groove l6 ofthe drill. Welded connections l8 attach the bodies firmly to the drill.

The formations l2 project laterally of the drill in diametricallyopposite directions distances such as to provide a countersunk hole ofthe desired diameter, the distances varying with respect to drilldiameters. Each formation has an outer rounded face 20 tapering to thediameter of the drill and in the direction ofthe shank thereof.

The end faces 22 of the formations l2 converge toward the cutting end ofthe drill and terminate in cutting edges 24 angled to out thecountersunk hole with the correct taper.

A countersinklng drill in accordance with my invention requires arelatively small amount of material. The two steel formations aresecurely attached to the drill and are so located as not to impair thedrill for ordinary drilling purposes.

Without further elaboration, the foregoing will so fully illustrate myinvention, that others may, by applying current knowledge, readily adaptthe same for use under various conditions of service.

I claim:

A countersink drill comprising a bit formed with spiral grooves havingtheir inner extremities gradually merging into the surface of the shankportion thereof, and an elongated countersink cutter body fixedly seatedin the outwardly sloping portion of the inner extremity of each of thegrooves, the outer cutting end of the body being substantially circularin cross-section and disposed at an angle to the axis of the bitcorresponding to the angle of clearance at the outer end of 'the latter,the outer side of the body being substantially cylindrical and slopingupwardly and inwardly to merge into the surface of the shankcoincidently with the groove.

DOUGLAS H. FREESE.

